Experts agree, however, that the combination of cannabis and alcohol raises the chance of crashing more than either substance by itself. In a study of 1,882 motor vehicle deaths, the U.S. Department of Transportation found an increased accident risk of 0.7 for cannabis use, 7.4 for alcohol use, and 8.4 for cannabis and alcohol use combined.
Links
[1] http://www.prnewswire.com/news-releases/research-shows-that-any-dose-of-alcohol-combined-with-cannabis-significantly-increases-levels-of-thc-in-the-blood-300089419.html
[2] http://rethinkpot.org/tags/alcohol
[3] http://rethinkpot.org/tags/research
[4] http://rethinkpot.org/tags/vehicle-0